CCSD(T) study of the far-infrared spectrum of ethyl methyl ether

10 pages, 5 figures, 9 tables.Band positions and intensities for the far-infrared bands of ethyl methyl ether are variationally determined from a three-dimensional (3D) potential energy surface calculated with CCSD(T)/cc-pVTZ theory. For this purpose, the energies of 181 selected geometries computed optimizing 3n−9 parameters are fitted to a 3D Fourier series depending on three torsional coordinates. The zero point vibrational energy correction and the search of a correct definition of the methyl torsional coordinate are taken into consideration for obtaining very accurate frequencies. In addition, second order perturbation theory is applied on the two molecular conformers, trans and cis-gauche, in order to test the validity of the 3D model. Consequently, a new assignment of previous experimental bands, congruent with the new ab initio results, is proposed. For the most stable trans-conformer, the 30, 29, and 28 fundamental transitions, computed at 115.3, 206.5, and 255.2 cm−1, are correlated with the observed bands at 115.4, 202, and 248 cm−1. For the cis-gauche the three band positions are computed at 91.0, 192.5, and 243.8 cm−1. Calculations on the −d3 isotopomer confirm our assignment. Intensities are determined at room temperature and at 10 K. Structural parameters, potential energy barriers, anharmonic frequencies for the 3n−9 neglected modes, and rotational parameters (rotational and centrifugal distortion constants), are also provided.This work has also been supported by the Ministerio de Educación of Spain, Grant No. AYA2005-00702 Plan Nacional I+D+I 2004–2007 , CONACYT of Mexico, Grant No. 58728 CoNaCYT, and Computing resources of CESGA.Peer reviewe

Small linear carbon chains: vibrational and electronic states

First General Meeting in Prague, May 25 - 29, 2015The study of carbon chains type Cn and their ions has been attracted a significant effort due to their connection with the astrophysical observations, because pure carbon chains are abundant species in several sources such as the carbon rich circumstellar envelopes. In addition, they can play important roles in the reactivity of large systems containing carbon atoms. Carbon molecules have been considered responsible of the Diffuse Interstellar Bands (DIBs) [1]. Small chains are building blocks of larger species such as the fullerenes and the PAHs. In spite of their astrophysical relevance, few bare chains have been observed in gas phase extraterrestrial sources. The shortest chain C2, was the first detected, followed by C3 and the linear-C5 [2-3]. Detections were performed through the analysis of Infra-Red active vibrational excitations or through their electronic transitions because they present a zero dipole moment. All the Cn chains present a large number of isomers, however, in this work we focus on the linear ones. The large stability of charged linear chains was used as argument to predict the presence of anions in the interstellar medium. We present computed molecular properties calculated using highly correlated ab initio methods (CCSD(T)-F12, MRCI/CASSCF). We determine structures, infrared frequencies and excitations energies to the lowest electronic states and electron affinities of the small chains type Cn (n=3,4,5,6,7). Special attention is given to the anions which relevance for reactivity is evident. Non-adiabatic effects and spin-orbit effects will be predicted.Peer Reviewe

La aplicación de las bases de datos al periodismo

El objetivo de este análisis no es sólo acercarse a la naturaleza de las bases de datos (aproximación que consideramos obligada para entender, en el momento en que nos encontramos, cuál es la presencia de este tipo de Información digital y qué amenazas sufre por parte de otros soportes, como puede ser el cederrón, o nuevos medios de distribución, en el caso de la mencionada Red), sino desentrañar y cuestionar su utilización por parte del Periodismo, que se ha encargado de limitar el empleo de estas recopilaciones a una nueva parcela del mismo denominada como Periodismo de Precisión

Is the Fast Evolution Scenario for Virialized Compact Groups Really Compelling? The Role of a Dark Massive Group Halo

We report on results of N-body simulations aimed at testing the hypothesis that galaxies in X-ray emitting (i.e., virialized) Compact Groups are not tidally stripped when they are embedded in a common, massive, quiescent dark matter halo. To disentangle the effects of interactions from spurious effects due to an incorrect choice of the initial galaxy model configurations, these have been chosen to be tidally-limited King spheres, representing systems in quasi-equilibrium within the tidal field of the halo. The potential of the halo has been assumed to be frozen and the braking due to dynamical friction neglected. Our results confirm the hypothesis of low rates of tidal stripping and suggest a scenario for virialized Compact Group evolution in their quiescent phases with only very moderate tidally induced galaxy evolution can be generally expected. This implies the group stability, provided that the dynamical friction timescales in these systems are not much shorter than the Hubble time. We discuss briefly this possibility, in particular taking account of the similarity between the velocity dispersions of a typical virialized Compact Groups and the internal velocity dispersion of typical member galaxies. A number of puzzling observational data on Compact Groups can be easily explained in this framework. Other observations would be better understood as the result of enhanced merging activity in the proto-group environment, leading to virialized Compact Group formation through mergers of lower mass halos, as predicted by hierarchical scenarios of structure formation.Comment: 18 pages, 1 postscript file, 2 tables, to be published in ApJLet

Shape and kinematics of elliptical galaxies: evolution due to merging at z < 1.5

[EN]Aims. We investigate the evolution in the shape and kinematics of elliptical galaxies in a cosmological framework. Methods. We identified relaxed, elliptical-like objects (ELOs) at redshifts z = 0, z = 0.5, z = 1 and z = 1.5 within a set of hydrodynamic, self-consistent simulations completed for a concordance cosmological model. Results. The population of elliptical systems that we analysed evolve systematically with time becoming rounder in general by z = 0 and also more velocity dispersion supported. We found that this is due primarily to major dry mergers where only a modest amount of angular momentum is involved in the merger event. Despite the general trend, in a significant number of cases the merger event involves a relatively high amount of specific angular momentum, which causes the system in general to acquire higher rotational support and/or a more oblate shape. These evolutionary patterns persist when we study our systems in projection, in simulating true observations, and thus should be evident in future observations.Peer reviewe

Theoretical analysis of the voltage unbalance factor to characterize unbalance problems in induction motors

Voltage Unbalance (VU) is one of the most common power quality problems in industrial electrical systems and it is a subject of systematic study. This problem affects the operation and the efficiency of Induction Motors (ims), which are the loads that demand more energy in the industrial sector with around 68%. The Voltage Unbalance Factor (VUF), defined by the international IEC standard, is the main factor used to characterize this problem. This article aims to present a theoretical analysis of VUF focused on its limitations for characterizing the effects of VU on ims. As a result of the analysis, it is shown that the use of the VUF indicator only is insufficient since it does not consider other aspects that affect the operation of the ims such as voltage variation. As an alternative, the use of the Complex Voltage Unbalance Factor and the Equivalent Voltage Magnitude Factor are suggested as parameters that, together with the VUF, allow deepening the characterization of the effects of the UV on the ims

Changes in the composition and function of bacterial communities during vermicomposting may explain beneficial properties of vermicompost

Vermicomposting is the process by which organic waste is broken down through the synergistic actions of earthworms and microbial communities. Although vermicomposting has been shown to effectively reduce organic biomass and generate high-quality fertilizer for plants, little is known about the bacterial communities that are involved in this decomposition process. Since optimization of vermicomposting for commercial use necessitates additional knowledge of the underlying biological processes, this study sought to characterize the bacterial succession involved in the vermicomposting of Scotch broom (Cytisus scoparius), a leguminous shrub that has become invasive around the world with consequences for the dynamics and productivity of the ecosystems they occupy. Scotch broom was processed in a pilot-scale vermireactor for 91 days with the earthworm species Eisenia andrei. Samples were taken at the initiation of vermicomposting, and days 14, 42 and 91, representing both active and mature stages of vermicomposting. Significant changes (P < 0.0001) in the bacterial community composition (richness and evenness) were observed throughout the process. Increases in taxonomic diversity were accompanied by increases in functional diversity of the bacterial community, including metabolic capacity, streptomycin and salicylic acid synthesis, and nitrification. These results highlight the role of bacterial succession during the vermicomposting process and provide evidence of microbial functions that may explain the beneficial effects of vermicompost on soil and plants.Ministerio de Economía y Competitividad | Ref. CTM2013-42540-RMinisterio de Economía y Competitividad | Ref. AGL2017-86813-RXunta de Galicia | Ref. ED431B 2016/043Xunta de Galicia | Ref. ED431F 2018/05Ministério da Educação e Ciência | Ref. IF/00764/2013Ministerio de Economía y Competitividad | Ref. RYC-2016-2123